Pleural fluid exudates are characterized by which features?

Pleural fluid exudates are characterized by which features?

• A. All of these
• B. A total protein fluid to serum ratio of 0.7
• C. Reflect primary involvement of the pleura
• D. An increased LDH fluid to serum ratio

Answer: (A)

Exudative pleural effusions arise from local pleural disease that makes vessels leak more protein and enzymes into the fluid. Light’s criteria are used to identify exudates and hinge on comparing pleural fluid constituents to serum. If the protein ratio (pleural fluid to serum) is above 0.5, that already favors an exudate; if the LDH ratio (pleural fluid to serum) is above 0.6, that also supports an exudate; and if pleural fluid LDH is higher than two-thirds the upper limit of normal serum LDH, that too indicates an exudative process. A protein ratio of 0.7 meets the first criterion, showing the fluid is protein-rich. An increased LDH ratio aligns with the second criterion, reflecting higher enzymatic content in the fluid. Finally, exudates reflect disease localized to the pleura—inflammation, infection, malignancy—rather than a systemic factor. Taken together, these features describe an exudative effusion, so all three statements fit.

Exudative pleural effusions arise from local pleural disease that makes vessels leak more protein and enzymes into the fluid. Light’s criteria are used to identify exudates and hinge on comparing pleural fluid constituents to serum. If the protein ratio (pleural fluid to serum) is above 0.5, that already favors an exudate; if the LDH ratio (pleural fluid to serum) is above 0.6, that also supports an exudate; and if pleural fluid LDH is higher than two-thirds the upper limit of normal serum LDH, that too indicates an exudative process. A protein ratio of 0.7 meets the first criterion, showing the fluid is protein-rich. An increased LDH ratio aligns with the second criterion, reflecting higher enzymatic content in the fluid. Finally, exudates reflect disease localized to the pleura—inflammation, infection, malignancy—rather than a systemic factor. Taken together, these features describe an exudative effusion, so all three statements fit.